Orians, K, , University of British Columbia, Vancouver, Canada, orians@eos.ubc.ca

THE RELATIONSHIP OF Cu CONCENTRATIONS INFERRED BY ASV AND DGT TO Cu UPTAKE ON FISH GILLS IN SOLUTIONS WITH AN EXCESS OF STRONG LIGANDS

Quantification of a “labile” fraction of metals in solution can be carried out by a variety of approaches, each of which detects a different, operationally defined fraction of the “dissolved” concentration. In two sets of experiments, labile metal concentrations were inferred by both ASV and DGT. In the first experiments, Cu concentrations were determined on freshwater solutions in the presence of an excess of either EDTA or NTA. The labile concentrations determined by ASV were similar to the concentrations of inorganic species predicted by MINEQL+. However, the concentrations determined by DGT were significantly higher, indicating that the DGT device sequesters significantly more than the inorganic species that exist at equilibrium. In the second set of experiments, freshwater solutions were created with 10 mg/L DOC from four different natural sources and Cu concentrations ranging from 0 to 3.2 micromolar. Again, the concentrations inferred by DGT were considerably higher than those measured by ASV. However, the patterns of Cu uptake by the gills of rainbow trout bore a strong resemblance to the pattern of Cu concentrations inferred by DGT.